“Muckrakers” were reporters who, exploiting mass circulation journalism, attacked malfeasance in American politics and business. President Theodore Roosevelt gave them the name “muckrakers,” after a character in the book Pilgrim’s Progress, “the Man with the Muckrake,” who was more preoccupied with filth than with heaven. Popular magazines such as McClure’s, Everybody’s, Pearson’s, Cosmopolitan, and Collier’s published articles exposing the evils of American society—political corruption...